I'm no browser architect--I don't know how the rendering engines compare, and of course it depends on the site and the extensions used. I did just time some popular websites, and confirmed my impressions. For example, nytimes.com gives
That was in private windows with no extensions. I tried it on my Windows machine with no extensions too, and it was 1.44 to 1.51, basically margin of error. I know MacOS Firefox has really lagged on performance improvements in the past. It could be a Mac-only issue.
0.5s on Safari with Adguard
1.6s on Chrome with uBlock Origin
2.5s on Firefox with uBlock Origin
which is pretty representative.